Effect of Relative Humidity on the Electrospinning Performance of Regenerated Silk Solution

Recently, the electrospun silk web has been intensively studied in terms of its biomedical applications, including tissue engineering scaffolds, due to its good biocompatibility, cytocompatibility, and biodegradability. In this study, the effect of relative humidity (RH) conditions on the morphology of electrospun silk fiber and the electrospinning production rate of silk solution was examined. In addition, the effect of RH on the molecular conformation of electrospun silk web was examined using Fourier transform infrared (FTIR) spectroscopy. As RH was increased, the maximum electrospinning rate of silk solution and fiber diameter of the resultant electrospun silk web were decreased. When RH was increased to 60%, some beads were observed, which showed that the electrospinnability of silk formic acid solution deteriorated with an increase in RH. The FTIR results showed that electrospun silk web was partially β-sheet crystallized and RH did not affect the molecular conformation of silk.

A study on the coordination of cyclohexanocucurbit[6]uril with copper, zinc, and magnesium ions

Herein, we report the supramolecular complexes of cyclohexanocucurbit[6]uril (CyH6Q[6]) with Cu(ClO4)2, Zn(ClO4)2, and Mg(ClO4)2 in formic acid solution. The crystal structure was determined using single crystal X-ray diffraction. The analysis results showed that CyH6Q [6] formed a one-dimensional supramolecular chain with Cu(ClO4)2 and formed a supramolecular assembly with a mixture ratio of 2:3 with Zn(ClO4)2 and Mg(ClO4)2. In this system, ClO 4 − {\text{ClO}}_{4}^{-} induced CyH6Q[6] and metal ions to form supramolecular complexes through ion–dipole interactions.

INVESTIGATION OF THE POSSIBILITY OF USING THE LIQUID SURFACE AS AN ELECTRODE FOR COLLECTING PRODUCTS OF CHEMICAL REACTIONS OCCURRING IN THE ELECTROSPRAY TORCH MICRODROPLETS

The present work is devoted to the study of the possibility of electrospray onto the surface of a liquid in order to accumulate the products of reactions occurring in micro- and nanodroplets of the electrospray torch. The experimental device was made for research purposes. A stable mode of electrospray of a water-ethanol mixture (1:4) onto a liquid electrode (water-ethanol mixture (1:4)), without using sputting gas, was obtained at a spray voltage U of at least 4 kV and a distance between the spray needle and the surface of the liquid R of no more than 15 mm. The spray current increased as the distance between the spray needle and the surface of the liquid electrode decreased and the spray voltage increased. A stable mode of electrospray of the reaction mixture (4 ml of a mixture of acetonitrile and 0.2 % formic acid solution in water (1: 1), 0.5 ml of aniline and 0.5 ml of acetone) onto the surface of the liquid electrode (mixture of 6 ml of acetonitrile and 6 ml of 0.2 % formic acid solution in water or a mixture of 6 ml of acetonitrile and 6 ml of water) with the use of the sputting gas was obtained with the following values of the parameters of the experimental device: the flow rate of the spray solution Qp = = 100 μL / min, the spray voltage U = 3.2 kV, the distance between the surface of the liquid electrode and the spray needle R = 35 mm. The maximum flow rate of the sputting gas was 2 L/min. Unreacted substances and the chemical reactions products of the components of the sprayed reaction mixture accumulated in the liquid electrode when the given values of the parameters of the device were used. This was confirmed by spectrophotometric measurements.

Corrosion of carbon steel in formic acid as an organic pollutant under the influence of concentration cell

The presence of contaminants in water even in small amounts can cause considerablecorrosion damages of metals. This is due to free corrosion effect or the formation ofconcentration cell of pollutants resulting in a galvanic effect. The current work was devotedto study the effect of formic acid (CH2O2) as an organic pollutant on the corrosion rate ofcarbon steel under different operating conditions. It includes an investigation of galvaniccorrosion caused by the establishment of concentration cell of formic acid under differentoperating conditions. The ranges of operating parameters were formic acid concentration of10-4 - 10-5 M and temperature of 32 - 50 °C. The results showed that increasing formic acidconcentration to 10-4 M leads to an increase in the corrosion rate by up to 7.6 times that inthe water of 0.1N NaCl. In addition, the corrosion rate in each terminal in concentrationcell also increased by up to 2.3 times. Pumping of air in formic acid solution led to aconsiderable increase in the corrosion rates and enhances the concentration cell effectwhich increases the galvanic currents. High increase of corrosion rate was noticed bypumping the air at high temperature reaching up to 4 times depending on temperature. Ingeneral, the galvanic currents were high initially and decreased with time due to theformation of corrosion product layer. The increase in temperature from 25 to 50 oC causedan increase in the galvanic corrosion rate reached up to 2 times in formic acid solution. Inaddition, the galvanic currents were noticed to decrease with temperature while thecorrosion rate of each terminal was increased.

A Simple and Rapid High-Performance Liquid Chromatography—Photodiode Array Method for Quantitation of Triacetin Contents From 30 Batches Produced in China

In our present study, the standard chemicals of triacetin were purified by reverse-phase and normal-phase semi-preparative high-performance liquid chromatography (HPLC), and 1H NMR and 13C NMR were employed to determine the purity and structure of triacetin. Moreover, a simple and rapid HPLC-photodiode array (PDA) method was developed to determine the contents of triacetin in 30 batches from different suppliers. The chromatographic separation was performed on a Phenomenex Gemini-NX C18 column (250 × 4.6 mm, 5 μm) using a gradient elution system of water and acetonitrile (contained 0.1% of formic acid) solution with a flow rate of 1.0 mL/min at 30°C at 210 nm. Sample preparation method is rapid and energy efficient, and the obtained sample have a good purity. Validation shows good specificity, linearity (R2 = 0.9995), precision, stability, repeatability (% RSD < 2.80) and the average recovery (99.72%) of triacetin. The content of triacetin in most samples is concentrated in 94–97%. This developed approach is simple, rapid, accurate and can be used to quickly determine the purity and the content of triacetin in plasticizers and filter plugs.

Simultaneous determination of sibutramine and its derivatives in weight loss dietary supplements by LC-MS/MS

The liquid chromatography tandem mass spectrometry method (LC-MS/MS) was used to determine the content of sibutramine (SB), N-desmethyl sibutramine (DSB) and N-didesmethyl sibutramine (DDSB) illegaly mixed in weight loss dietary supplements. Sibutramine and its derivatives were extracted by methanol; impurities in the extract were removed by graphitized carbon black (GCB) adsorbent. The chromatographic separation of analytes took place on C18 column (100 mm x 2.1 mm, 3.5 µm) with a gradient mobile phase of acetonitrile and 2 mM ammonium acetate in 0.1% formic acid solution. Multiple reaction monitoring (MRM) in the positive mode was used to detect and quantify SB, DSB and DDSB at m/z 279.9/124.8; 266.0/124.8 and 252.1/125.0, respectively. The method was validated following the AOAC requirements for specificity, repeatability and recovery. Calibration curves lineared from 0.002 to 0.1 µg/mL for SB, DSB and DDSB. The method was successfully applied to determine the content of SB, DSB and DDSB in weight loss dietary supplements that were randomly collected from phamacies in Hanoi of three formulations of hard capsule, soft capsule and teabag. The results shown that six samples had SB and DSB with the content in the range of 0.817 - 31.7 mg/g.

Utilization of White Glutinous Rice Fermentation as A Coagulant of Natural Rubber Latex

Clumping is one of the important stages in the processing of latex. This stage is the first step to produce a coagulum. The purpose of this study was to determine the potential of white sticky water tape as a latex coagulant and determine the effect of white sticky water tape on the speed of clumping, color, pH, texture, levels of latex dry rubber. Tests were carried out in 4 treatments, namely R0: 1 ml of 10% formic acid solution added to 100 ml of latex; R1: 1 ml of water tape is added in 100 ml of latex; R2: 5 ml of water tape is added in 100 ml of latex; R3: Water tape as much as 10 ml was added to 100 ml of latex Then the latex parameters were observed including clumping speed, pH, texture, color and levels of dry rubber (KKK). The results of this study indicate that the administration of white sticky tape water does not reduce the pH of the latex to the isoelectric point 4.7. Nevertheless latex clumping still occurs. This is thought to be due to the alcohol content in the white sticky water tape. Based on observations, the R2 treatment is the best treatment that produces a slippery and hard coagulant texture similar to the R0 (formic acid) treatment. Whereas the latex texture in R1 and R3 treatments is softer. The addition of white sticky tape water coagulant produces latex color to milky white while formic acid produces white-yellowish color. The R2 treatment had an average KKK 41.63% lower than using formic acid, which was R0 45.96%. Although the white sticky tape water coagulant has not been able to meet the KKK quality standards of 20%.

Deproteinization as a Rapid Method of Saliva Purification for the Determination of Carbamazepine and Carbamazepine-10,11 Epoxide

Saliva is a valuable diagnostic material that, in some cases, may replace blood. However, because of its different composition, its use requires the development of new, or the modification of existing, extraction procedures. Therefore, the aim of the study was to develop a method of saliva purification that would enable the determination of carbamazepine and its metabolite, carbamazepine-10,11 epoxide. When comparing two methods of sample purification (Solid Phase Extration (SPE) and deproteinization), it was found that the second method yielded more favorable results. A 1% formic acid solution in acetonitrile was used for extraction. The samples were shaken and centrifuged, and the supernatant obtained was evaporated and dissolved in a mobile phase, then chromatographically analyzed. The developed method was validated by determining its linearity in the range of 10–5000 ng/mL for both analytes. Intra- and inter-day precision did not exceed 14%. In order to check the usefulness of the method, both analytes were determined in the saliva samples from 20 patients treated with carbamazepine. The content of both analytes was detected and determined in all of the tested samples of saliva. It was found that the method developed is rapid, sensitive, reliable, and can be used to monitor the concentration of carbamazepine and metabolite in patients’ saliva.

Analysis of Amoxicillin and Tetracycline Residues in Chicken Meat Using High Performance Liquid Chromatography-Mass Spectrometry

Antibiotics are commonly used as food additives in broiler farms and their use tends to be excessive regardless and incorrect that can leave some antibiotic residues in chicken meat. The aimed of this study was to analyze on antibiotic residues level amoxicillin and tetracycline in chicken meat sold in Medan. The antibiotic residues analysis was conducted by extracting the antibiotic from chicken meat with water and acetonitrile (2:8, v/v) and detected by high performance liquid chromatography-mass spectrometry detector using C-18 column (4.6 mm i.d., length 30 mm, particle size 1.8 µm) at 35 oC, with the mobile phases, 0.1 % formic acid solution in water and 0.1 % formic acid solution in methanol with gradient elution technique at a flow rate of 0.5 ml/minute. The result exhibited that the chicken meat that were collected from five markets in Medan apparently contained antibiotic residues tetracycline . The level of tetracyclin residue in chicken meat was 0.1157-1.4436 µg/g, which exceed the maximum level for tetracyclin residue allowed in foodstuffs of animal origin which is 0.1 ug/g. Keywords: residue, antibiotic, amoxicillin, tetracycline, chicken meat